In conventional shaft systems, cylindrical bearing sleeves may be mounted around rotating shafts. A bearing housing surrounds the shaft and bearing sleeve and has several bar shaped, substantially trapezoidal cross-section cavities in which stave bearing inserts are installed. The bearing surfaces of the stave bearing inserts bear upon the rotating shaft sleeve and thereby hold the rotating shaft in a fixed position against sideways movement.
Stave bearing inserts are made of materials that perform best when they are in contact with a smooth cylindrical sleeve. If the bearing sleeve surfaces wear unevenly, the sleeves must be repaired and machined to having a smooth cylinder surface. When the sleeve wall gets too thin it must simply be replaced.
Shaft sleeves can be machined in place to polish and repair their surface if enough clearance is available to fit a portable machining device. The process involves dismantling the entire bearing assembly, installing the portable machining device, and then removing enough material from the sleeve to make a clean and smooth cylindrical surface. New bearing inserts are then machined to fit the new sleeve diameter. Alternatively, the entire shaft can be removed and transported to a machining facility to have the sleeve machined or replaced. This is a major expense and typically involves months of downtime, and major outage losses.
As stave bearing inserts wear out, they often cut circular grooves around the bearing sleeve and scratch the sleeve surface. The unit is then taken out of service awaiting repair for an indefinite period and corrosion and other buildup on the sleeve surface occurs.
If instead scratches, corrosion and other buildup on the shaft sleeves can be smoothed out in place, new stave inserts can be installed which will perform well for years bearing only the high spots between the circular grooves on the sleeve. It is not feasible to clean and polish the sleeves by hand and achieve a satisfactory result.